(1) Field of the Invention
The present invention relates to monolithic photoreceiver technology.
(2) Brief Description of Related Art
The next logical extension to the Internet is a free space mobile digital data network that is pervasive and can meet both commercial telecommunications' need for ubiquitous connectivity and need to provide the war-fighters with assured and secure information anywhere, at any time, and in the right form, using an extensible communication architecture that assures maximum connectivity among the current terrestrial networks, the battlefield, aircraft, spacecraft, Unmanned Vehicles (UAVs), ships and submarines. Of all the candidate technologies, free space mobile optical communications is considered the most likely to enable the highest data rate, longest range and highest sensitivity.
To achieve connectivity to other terminals in the theater and the needed bit rate of greater than 2.5 Gb/s, the notional free space mobile optical data network will require powerful and efficient optical transmitters at the basic physical layer level, as well as ultra-sensitive photo-receivers. Widespread deployment of such a network will require paradigm shifts in the development and production of optical networking devices and components that will minimize size, weight, power and system cost, while meeting all network link performance requirements.
Free Space Optics (FSO), also known as Optical Wireless communication has become a viable, high bandwidth solution to, fiber optic, millimeter wave wireless and RF technologies. The main disadvantage of FSO is atmospheric attenuation, which is weather dependent. Therefore, in order to address the atmospheric attenuation either link distance or link budget has to be compromised. Increasing the link budget will not be cost effective and also increases the size, weight and power (SWaP). A more practical solution which would extend the link distance keeping the link budget constant or increase the link budget keeping the link distance constant would be to develop ultra-sensitive receiver technology. For example, the potentially incident optical radiation can be as low as −40 dBm (100 nW), the notional network requires photoreceivers with sensitivities as low as −47 dBm(1). Although there have reportedly been bench level demonstrations of direct detection photo-receivers employing erbium doped fiber amplifier (EDFA) technology that have comparable performance, there are no compact, affordable, and commercially available photo-receivers that will meet these requirements(2,3).